I personally do not think ADS-B on the helicopter would have changed anything , From what I understand , if it had it could have been spotted earlier by ATC , the conflict alert might have sounded a couple of seconds earlier , etc .. pure speculation .
It would not have changed much for the AA CRJ either , the TA would have been more precise and maybe a second or two earlier , but he had already 2 TAs and most certainly so short from landing the PF was focusing on the PAPI not his TA display
It might have changed something if the Heli was equipped with a CDTI ( ADS-B in display) as it is a powerful tool to help identify traffic visually. But not separate yourself from another aircraft . One thing people in offices making such statements forget is that to provide separations maneuvers ATC needs a stable radar picture , with antennas firmly on the ground facing North . Inside an aircraft constantly moving the picture moves with it , (as you can see on your TCAS display ) Extremely complex to separate yourself using that kind of picture when both you and the target are moving. AWACS operators are trained to do this , but not your average pilot .
So I think this ADS-B on the Military Helis is a red herring made by politicians wanting to appear to “do something “ and perhaps distract the public from the FAA and regulator failures on both the design of the airspace / routes and the lack of action after numerous previous serious incidents reports ,